The thing about Tyson, he fought like a small fighter. He certainly had flaws, like being much too willing to fall into clinches and let a bigger man lay on him. But, by and large, he fought fast. he started outside, closed quickly and did lots of damage on the way in. His hands were as fast as anybody that has ever been a HW; his feet were real fast as well.
When you consider him against the all-time heavyweights...I don't think he would beat Joe louis because Louis threw such concise powerful punches. He was very fast with his hands as well, and shorter; he'd catch Tyson coming in. Of course, the speed and power of Tyson could make all that irrelevant, but I think louis would beat him.
I think Tyson would beat Ali, and have the easiest time against the 'prime' Ali. Because the way Ali would fight, with movement and jabs, was all all all wrong against Tyson. First, you ain't gonna beat Tyson, at his best, with a jab. His whole freaking game was getting around a jab. They knew he was a short HW and programmed him accordingly. Now, if you jab, or feint the jab, and counter off his reaction, you can get some action.
But to jab and move? Foolish. That would let him get up steam, start taking those crossover steps (watch tape and see how often he would step over, to his right, end up in a southpaw stance and punch effectively from there)and landing punches from odd angles. he'd beat Ali easy. He'd have more trouble with the older, slower, clutch and grab Ali.